This invention pertains to surgical lamps and more particularly is concerned with light reflectors for such lamps. Modern surgical practice calls for artificial light sources to illuminate the surgical area with broad spectrum light to assure accurate color. A tungsten-halogen bulb, for example, emits the full range of desired visible light, but will also emit undesirable ultraviolet and infrared radiation. Undue exposure to either bands could burn the tissue of the patient and the surgeon. The tungsten-halogen bulb may be surrounded by a material which absorbs most of the ultraviolet radiation, but the infrared radiation must be allowed to pass to avoid excessive heat buildup close to the bulb. Light is emitted omni-directionally from the bulb, so a reflector is used to direct the light to a surgical area. Polished aluminum and other metals have been used as reflector materials, but are deficient as they reflect infrared radiation to the surgical area. Heat resistant glass is now used as a reflector material in most surgical applications. The glass is coated with a dichroic material which reflects visible light towards the patient but transmits infrared light harmlessly out the back of the lamp. The glass must also be molded to an appropriate shape and must be both temperature and shatter resistant. Suitable glass is a dense and expensive material. Furthermore, an expensive clamp arrangement may be used to secure a glass reflector to the surgical lamp. It would be of benefit to both the manufacturer and the purchaser of surgical lamps for the weight and cost of reflectors to be successfully reduced, yet still provide the high performance required for such an appliance.
It has been suggested to use polycarbonate, polyphenylene sulfide, and polysulfone for reflectors. Each of these plastic materials has been found to have properties which distracts from its usefulness as a surgical lamp reflector.
Polycarbonate cannot tolerate the 140.degree. C. temperature a reflector is exposed to and this material was quickly removed from consideration.
Polyphenylene sulfide and polysulfone meet the temperature requirements, but both materials are sensitive in different degrees to ultraviolet light. Because of this reason, it is necessary to apply an ultraviolet absorbing base coat on the face of the reflector prior to the deposition of the dichroic coating. The base coat also provides better adhesion for the dichroic coating which would otherwise require a high surface temperature during deposition.
It is the object of the invention to provide a relatively low cost, low density plastic reflector for use in surgical lamps without the need of an ultraviolet absorbing base coat.